A temperature sensor detects a temperature of a temperature detection target such as a mold for forming a resin-molded product or a heating furnace for heating various products or the like. Such a temperature sensor may be of a type in which a temperature of the temperature detection target is detected by a thermocouple having a pair of wires.
The temperature sensor includes a temperature detector functioning as a temperature measuring unit having a cylindrical fixing body to which a part of the thermocouple is fixed. The temperature detector is provided at a target portion of the temperature detection target. The thermocouple has a pair of wires made of two different metals, e.g., alumel (a nickel/aluminum alloy containing nickel as a main component) and chromel (a nickel/chromium alloy containing nickel as a main component).
In the temperature sensor, one end of each wire is fixed to one end of the cylindrical fixing body by a welding material, e.g., silver or the like. A thermoelectromotive force is generated based on a thermoelectric power difference between two wires, and thus current flows in a constant direction. A temperature of the target portion of the temperature detection target is detected from the flowing current.
As for a conventional temperature sensor having such a thermocouple, there is known one in which two holes are formed at a leading end portion of the cylindrical fixing body (supporting cylinder) and wires forming a thermocouple are inserted into the holes and fixed by welding (see, e.g., Japanese Patent No. 4177333)
However, in the temperature sensor described in Japanese Patent No. 4177333, the two holes are formed at the cylindrical fixing body and the wires are inserted into the holes and adhered by welding. Therefore, the hole forming operation and the wire inserting operation into the holes are respectively performed twice. This increases the operation time, which leads to an increase of the manufacturing time and increases the manufacturing cost.
Further, depending on the thickness of the wire, the size of each hole needs to be greater than a specific size. The outer diameter of the cylindrical fixing body tends to be increased due to the multiple holes, which makes it difficult to achieve miniaturization.